The use of radiation to treat medical conditions comprises a known area of prior art endeavor. For example, radiation therapy comprises an important component of many treatment plans for reducing or eliminating unwanted tumors. Unfortunately, applied radiation does not discriminate between unwanted materials and adjacent tissues, organs, or the like that are desired or even critical to continued survival of the patient. As a result, radiation is ordinarily applied in a carefully administered manner to at least attempt to restrict the radiation to a given target volume.
Collimators are often used to restrict and form the radiation-therapy beam. Many collimators have a fixed aperture. Other collimators have an aperture that can be adjusted in one or more dimension. Adjustable apertures permit, to at least some degree, customization of the radiation-therapy beam's cross section to thereby attempt to better match the requirements of a given target volume. Multileaf collimators are an example of such a component. Multileaf collimators are comprised of a plurality of individual parts (known as “leaves”) that are formed of a high atomic numbered material (such as tungsten) that can move independently in and out of the path of the radiation-therapy beam in order to selectively block the beam.
It is also known to employ more than one collimator in conjunction with a single radiation-therapy beam. In a not untypical application setting, for example, the radiation source often has a primary collimator comprising shielding that essentially completely surrounds the source save for an output aperture (which is often circular in shape). A second collimator (sometimes referred to as a “jaws”) then serves to generally shape the beam while a downstream multileaf collimator then more specifically customizes the cross-section of the beam as described above.
Depending upon the specifics of a given target volume and/or the characteristics of a given treatment paradigm, prior art approaches in these regards can yield satisfactory results. In other cases, however, there is considerable room for improvement. In some cases, for example, these prior art approaches do not necessarily ensure an appropriately shaped beam at all times during a treatment session. In other cases, these prior art approaches do not yield optimum results within the time available for practical administration of the radiation therapy to a given patient.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.